Why did Krishna Leave Brindavan ?

I always had this doubt in mind, why did Krishna leave Brindavan ? After all everyone in Brindavan loved him immensely, infact they couldn't imagine their life without him and Krishna knew this, then why did he take such a harsh decision to leave them behind and move forward in his life. Somewhere this didn't seem right to me because it’s my belief that God doesn't leave people who love him purely and selflessly although he may give you troubles and miseries but he would always be there with you along the way protecting you. This brings me back to my question, Then why did Krishna leave Brindavan ? I believe I have uncovered this mystery today.

Today morning I was reading about Kaliya Mardanam in river Yamuna which I have read many times though but something’s didn't seem right to me this time.

When Krishna plunged into the river to kill Kaliya snake, nobody (friends, villagers, gopikas, etc...) dared to go along with him. They just left him alone to fight the big snake. This is just not it, I understand may be they were scared, but when Kaliya took Krishna under water and when Krishna didn't turn up for a long time even then none of the people could overcome their fear and dared to go in to rescue him. They were just standing on the banks and praying for him. This is not what I would call love, they were fearing about their life and were ready to sacrifice Krishna. This is no selfless love. In love the "I" don't exist, it’s just the other person. I believe Krishna realized it and may be to confirm it, he was waiting under water holding his breath just to see if somebody overwhelmed by his love would dare come in, but none did, not even Radha. This answered my another looming question in my mind, Why didn't Krishna marry Radha, if both of them were deeply in love with each other ? Krishna would have definitely married her, if she had jumped into the river ignoring herself to save Krishna, which she didn't. If you were truly in love with a person you would not let that person face trouble alone, even when you know the opponent is strong, you would still put a fight to protect your beloved.  So Krishna for Radha was just infatuation but not pure love. Most people reading this might not agree as most of us have been trained right from childhood to think Radha and Krishna as ideals, I somehow don't feel it that way anymore. 

This episode is what I think (could be others as well) made Krishna take such a harsh decision to move away from them. These people where dependent on him, they missed him, but there was no love involved there, it was just mere attraction. To justify my point, let’s see why he married Rukmini and Sathyabhama and why did he consider Arjuna to be his best friend.

Rukmini wanted to marry Krishna and surrendered herself to him, even if she had to go against her entire family, she did it and Krishna didn't leave her.

Sathyabhama didn't run away when Krishna was knocked unconscious by Narakasura, infact she fought even more bravely, defeated Narakasura and rescued Krishna. This explains every reason why Krishna respected her and listened to all her words.

Arjuna fought against his beloved Bheeshma, Drona and the rest just because Krishna said. No question asked.

I'm not concluding anything here, but leaving it to the readers to think about it and let me know their thoughts on this. 

For those who donot know the story of Kaliya Mardanam: http://www.balagokulam.info/purana-stories/kaliya-mardanam